Fig. 1: Schematic illustrations depicting the particle size dependent phase evolutions of olivine FePO4 particles during lithiation or sodiation.
From: Identifying critical features of iron phosphate particle for lithium preference
Different color codes denote different phases during lithiation or sodiation. Here, we grouped the particles based on their different phase evolution pathways upon lithiation and sodiation. Some previous works also witnessed some phase transformations, including solid solution (SS) transition during lithiation20,21,22,28, phase separation transition during lithiation25,26, SS transition out of structural equilibrium during lithiation27,28,29,30,31, and two-stage sodiation transition (phase separation + SS transition)32. In this work, we observed SS (out of structural equilibrium) transition upon sodiation. The dashed box in the diagram indicates the equilibrium SS transition throughout the range upon sodiation has not been observed experimentally.
